Piston wrist pin assembly



Dec- 29. 1953 M. A. ELLIOTT 2,664,327

PISTON WRIST PIN ASSEMBLY Filed Feb. 15, 1951 Fig.3.

Imventor: Marvel A. Elliott,

l-lis Attorneg.

Patented Dec. 29, 1953 UNITED STATES PATENT OFFICE PISTON WRIST PINASSEMBLY Marvel A. Elliott, Erie, Pa., assignor to General ElectricCompany, a corporation of New York My invention relates to compressorsand the like, more particularly to the wrist pin and con-' necting rodassemblies for pistons of compressors and the like.

In many presently used compressors, a wrist pin and connectin rodassembly is employed which includes a wrist pin positioned within anopening in a piston, and a spring biased tapered key disposed in alongitudinal passage in the wrist pin for connecting a connecting rod tothe wrist pin with some form of self-aligning or selfadjusting action.Heretofore, the spring member which biases the tapered key, byengagement with the larger end surface of the key, has been held incompressed condition within the longitudinal passage by some separatemember, such as a screw plug in threaded engagement with the walls ofthe longitudinal passage, or an arcuate spring clip snapped into aperipheral groove around the piston so as to cover the entrance to thelongitudinal passage.

The use of a screw plug involves the relatively costly operation ofthreading the plug and the inner surface of the longitudinal passage andalso causes difficulty in the assembly operation, since the spring mustbe compressed and held so while the screw plug is started into itsthreaded engagement.

The use of an arcuate spring clip involves the relatively high cost ofproviding the clip and machining a groove in the lower portion of thepiston. The clip and biasing spring are difficult to assemble since thebiasing spring must be compressed and held so while the spring clip issnapped into its receiving groove. Extreme care must be used in thisassembly operation because any set caused in the spring clip will makeit loose fitting enough so that it may rotate within the groove andrelease the biasing spring when the discontinuity between itsextremities reaches the entrance to the longitudinal passage.

It is, therefore, an object of my invention to provide an improved Wristpin and connecting rod assembly.

It is another object of my invention to provide simpler and less costlyretention means for a compressed biasing spring in a wrist pin andconnecting rod assembly.

In carrying out the objects of my invention, a wrist pin and connectingrod assembly including a tapered key is provided with a biasing springfor the tapered key which is formed with at least one turn on oneextremity thereof having a diameter greater than the diameter of theother turns. A longitudinal passage through the wrist pin is formed toinclude in one end thereof aportion of reduced diameter providing ashoulder. within the passage. When assembled, the tapered key isdisposed within the longitudinal passage of the wrist pin, passingthrough and wedging in an opening in the connecting rod. The key isbiased by the compressed spring to fasten the connecting rod and wristpin securely, with the turn at the smaller end of the spring bearingupon the surface of the larger end of the tapered key and thelarger turnof the spring bearing upon the shoulder.

The novel features and scope of my invention are pointed out with moreparticularity in the appended claims. For a better understanding of myinvention, however, together with further objects and advantagesthereof, reference should be had to the following description togetherwith the accompanying drawing.

In the drawing, Fig. 1 is a sectional elevational view of a pistontogether with the wrist pin and connecting rod assembly of my invention;Fig. 2 is a sectional elevational view illustrating a method ofassembling my invention; Fig. 3 is similar to Fig. 2, furtherillustrating the method of assembly; and Fig. 4 is a sectional viewtaken along line 4-4 in Fig. 2.

In Fig. 1, I have shown a compressor piston I with an associatedwristpin and connecting rod assembly including a wrist pin 2 and a connectingrod 3, which is only partly shown. The piston l is provided with atransverse passage 4 for receiving the wrist pin 2. In order to providefor connection of the connecting rod 3, the wrist pin 2 is provided witha longitudinal passage 5, including in one end thereof a portion 6 ofreduced diameter providing a shoulder 6', and a transverse passage 1extending from passage 5 downwardly through the bottom of the wrist pin.The bottom portion of the piston I is provided with a large opening 8for receiving the connecting rod 3 and permitting lateral movement ofthe connecting rod therein during operation of the compressor. The wristpin 2 is provided with an internal recess 9 located in line with passage1 for receiving the upper end it of the connecting rod. An opening llprovided in the connecting rod, which may be chamfered as shown, is thenin general alignment with passage 5 as shown.

In order that the piston I, wrist pin 2, and connecting rod 3 may bemaintained in assembled relationship, a tapered key I2 is disposedwithin passage 5 extending through opening I l. A spring [3 is disposedin compressed condition within passage 5 for urging key I2 toward theright as of passage trance to by portion as shown in the dr wing.

shown in the drawing, so that the key is in contact with the uppersurface of opening ii and the low-r surface of passage Thus, on theupward stroke of the piston, force is transmitted from end directly tothe upper surface of recess and on the downward stroke of piston, forceis from the upper surface of opening through key 52 to the lower surfaceAs any wear occurs between the connecting rod 3 and the wrist pin 2, theslack is immediately taken up by movement of key .42 to the right underthe biasing force of spring 53.

One or more of the turns at one end of springl3 (one turn is at the leftendheing illustrated) are of diameter substantially greater than thediameter the remainder of the turns so that spring is is held compressedby its smaller lend turn hearing against the larger end surface of keyis an" by its larger end turn it hearing aginst the shoulder 6. The sizeof key it is such that t mar easily he inserted into the enssage 5provided by the reduced diameter portion E. The turns of spring l3,except turn i i, are also of -such diameter that the right end or" thespring may also be insert-ed into that entrance. However, turn is of adiarnete larger than the entrance provided by portion 5 in order that itwill bear against shoulder 6 and hold spring is under compression after.ib'ly, the method of which is described hereafter.

A method of assembly for component such as those included. in the wristpin and connecting rod assembly of my invention best described by Way ofexample with reference to Figs. 2, 3 and l, and is as follows:

Wrist pin 2 is, of course, inserted into l as illustrated iii-Fig. 1 andthe connecting rod so that its end it rests in recess ey 52 theninserted, its smaller end first, through the entrance to passage 5provided by portion un til it engages connecting rod 3 as illustrated.Spring i3 is next placed, smaller end first, in a tapered sleeve, suchas sleeve 55, which'is with its smaller end in abutting alignment withthe entrance to passage 5 as shown by 2 and 3. A radially compressibleshaft-like tool. such as one including a hollow split shaft havingflexible tangs ii on one extremity thereof, is then used to push spring23 through sleeve E5. The smallest inside diameter of sleeve l 5,located at the right end thereof, is substantially the same size as thediameter of the entrance provided On the othe hand, the largest insidediameter of sleeve 55, located at the left end thereof, is at leastslightly greater than the diameter of turn i l when uncompressed. Theshaft at the flared extremity formed by tangs ll when uncompressed, issubstantially the same diameter as the end turn it when uncompressed.Thus, insertion of shaft is into sleeve l5 against spring causes thetangs ll to engage the turn it, as shown by the solid .lines of Fig. .2and illustrated more clearly by Fig. 4. Pushing shaft further intosleeve l5 advances the spring l3 and decreases the diameter formed bytangs I? and the end turn It, as shown by the dashed lines of Fig. 2.The spring i3 is thus pushed into passage 5 and turn it is radiallycompressed enough for it to enter the entrance provided by portion Oncepast the portion ii, theend turn ht e2 pands to engage the surfaceformed by shoulder 5 as illustrated by Fig. 3. The spring, by this s isinserted through opening 6 and passage '5 ffrom passage 5..

which means 4 method, is thus easily assembled into the corepressedposition hereinbefore described.

The larger end turn of sguin it may made to include lower 3 it it, asshown in which is one of the Wire forming spring ii Tail Ere portionextremity connecting rod assembly, the disaster hly method being simplyto reach through he entrance to passage 5 and grasp portion Eli wit: ofneedle-nose pliers; to turn portion terclockwise direction (as shownthat turn it is reduced in diameter engages shoulder 3; and then to putg l tapered key 5?. then he pushed out of passage and the rods pulledfrom opening 3.

My invention, therefore, pro simpler means for sorin in a Wrist pin andconnec VJhile the present in by reference to a pa uicuia it will beunderstood th made by those shined in departing from the in'ven in theappended aims cov t'iens as conic u iin the true 2,. of the foregoingclosure.

What I claim as new and desire to secure by Eet'tersPatent of'theUnitec. States is:

1. in a wrist pin and connecting rod assembly for compressors and thelike, a wrist pin a longitudinal passage therein, a portion of reduceddiameter at one end of said long,- udinal passage providing an entranceof reduced size to said longitudinal passage and shoulder within saidlongitudinal passage, said wrist haw 'ing a second passage thereinextending transversely from said longitudinal passage through theext=rior of said wrist pin, a connecting rod having a portion extendingthrough said second passage, said portion having an opening in generalalignment with said longitudinal. passage, a tapered key insertaolethrough said entrance posed within said longitudinal passage and extending into said opening in said portion of connecting rod, a springfor biasing said key to engagement with said connecting rod portionadjacent said opening, said spring having at least one turn at one endthereof of diameter greater than the smallest dimension of said entrancebearing upon said shoulder.

2. In a Wrist pin and. connecting rod assembly for compressors and thelike, a wrist pin havir a longitudinal passage therein, a reducedportion at one end of said longitudinal passage providing an entrance tosaid longitudinal passage smaller in transverse cross section than saidlongitudinal passage anda shoulder within said longitudinal. passage,said Wrist having a second passage. therein extending transversely fromsaid longitudinal passage through the exterior or said wrist pin, aconnecting rod extending through said second. passage and having anopening therethrough in general alignment with said longitudinalpassage, a tapered key insertahle through said entrance disposed Withinsaid longitudinal passage and extending through opening in saidconnecting rod, a helical spring for biasing said key to engagement withsaid connecting rod adjacent said opening, said spring having one turnlarger in diameter than the smallest dimension of :said entrance and theremander of turns smaller in diameter than the smallest dimension ofsaid entrance, said spring being disposed in compressed condition withone end thereof bearing against said key and the other end thereofbearing against said shoulder.

MARVEL A. ELLIOTT.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,152,876 Brown et a1 Sept. '7, 1915 1,480,185 Setter Jan. 8,1924 Number 6 Name Date Joseph Oct. 20, 1925 Thiry Nov. 10, 1931 CurtisAug. 8, 1933 Robertson July 23, 1935 Adams Aug. 28, 1945 .SteenstrupFeb. 5, 1946 Scheldorf Mar. 20, 1951 Kurtz May 29, 1951

